The present invention generally relates to phasing systems for continuous flow test systems and more specifically to an apparatus to enable completely automated blood sample testing.
In continuous flow systems in general and in blood-grouping machinery in particular, many individual samples are sequentially pumped through the same dividing, mixing, reaction and settling coils. The basic approach is to utilize the same tubing for processing many samples. The liquid reactants are propelled through the tubing in the systems by a metering pump system utilizing air bubbles to maintain separation between differing liquids. Typically, a sample which is segmented by several air bubbles will also be separated from the next sample by a wash solution. One example of such a continuous flow system is the Blood Grouping AutoAnalyzer manufactured by Technicon Corporation.
The Blood Grouping AutoAnalyzer makes use of the well known antibody-antigen reaction used in manual blood grouping. In "forward" grouping, well characterized antibodies contained in the sera of a known blood group are used as the reagent. These are reacted with unknown red cells contained in the sample. These red cells are obtained using a double sampling probe on a centrifuged whole blood sample. The upper probe samples the unknown plasma with the lower probe sampling unknown red cells. In "reverse" grouping, well characterized red cells ae used as the reagent. Unknown plasma from the upper probe is reacted with the reagent cells.
Regardless of whether forward or reverse grouping is performed, the mixing of red cells and plasma or serum is involved. The antibodies contained in the plasma or serum can attach to more than one red cell, and when they do, bridges are formed. When multiple bridges are formed, visible clumping of red cells or "agglutination" is noted. A reaction is termed positive if agglutination occurs. In the Blood Grouping AutoAnalyzer, a single sample is reacted with both known typing sera and known reagent cells in a parallel fashion. From the pattern of positive and negative reactions, the blood group and Rh factor can be established.
The currently available AutoAnalyzer equipment allows reactions to proceed to conclusion in a reaction manifold. At the end of each reaction coil contained in the manifold, a decant port in the bottom of the exit tube collects sedimented agglutinates. The output of the parallel reactant channels are then deposited on a moving belt of filter paper for subsequent manual interpretation. Unfortunately due to irregularities in glassware and pump tubing, the transit time for various reactant channels will differ. Clearly it would be ideal to have the output of each parallel reactant channel for a given blood sample simultaneously placed on a filter paper belt to facilitate comparison of the reaction products. The length of tubing connecting the output of a reactant channel with the moving belt of filter paper is generally varied such that all samples are in fact simultaneously applied to the moving filter paper.
Unfortunately, after several hundred samples, it is not uncommon for one or more channels to lead or lag the other channels very slightly such that towards the end of a three hundred sample batch, it would be unascertainable as to whether an agglutination reaction is attributable to sample 296 or 297 leading to inaccuracies and errors which are intolerable as far as the matching and categorization of human blood is concerned. These errors are generally overcome by virtue of the fact that a trained operator is necessary to visually categorize the reactions and tabulate the results and can factor out any lead or lag in the individual channel transit times.
In the past, various fully automated read out systems have been proposed with varying degrees of success. One such modification of the Blood Grouping AutoAnalyzer is described in "Automated Read Out of the BG-8 Blood-Grouping Machine" published in Vox Sanguinis, Vol. 30:445-452 (1976) subject matter thereof herein incorporated by reference. There a light emitting diode and a photo-diode sense the existence of a positive or negative reaction by virtue of the clarity or turbidity of the fluid passing through a clear tube located between the diodes located in the reaction stream after decantation of the agglutinates has occurred. In this scheme, the existence of a clear region in a reaction tubing is indicative of a positive reaction since the results of a positive reaction (agglutination) are removed (by decantation) before optical detection. In a subsequent publication "Automated Read-Out of Sample Identification and Test Results in a BG-8 Blood Grouping Machine," Vox Sanguinis, Vol. 33:108-115 (1977), a certain degree of success was reported although it was noted that synchronization was effected by varying the length of transmission tubing between the reaction channels and the optical sensor unit. However, this device would still require manual monitoring because due to the occurrence of protein deposits occurring in one or more of the channels, the synchronization of the system must be corrected each time a new tray of samples is installed for sampling. This necessity for resynchronizing the output of the sampler severely limits the "automated" aspect of the machinery and still requires a skilled technician for large volume operations.